1. Field of the Invention
The present invention relates to an illumination device, and more particularly to an illumination device capable of implementing a small-sized and high-efficiency projection system, and the projection system including the illumination device.
2. Discussion of the Related Art
Typically, an optical system for use in a projection engine can be mainly classified into an illumination system and a projection system.
The illumination system enables a light signal generated from a lamp to pass through an integrator or FEL (Fly Eye Lens), such that it uniformly applies the resultant light signal to a small-sized imager.
The projection system enables the light signal generated from the illumination system to be incident upon individual panels, magnifies the imager, and forms an image on a screen.
In this case, the most important performance of the above-mentioned projection engine is how the light signal generated from the light source is effectively focused on the imager.
In the meantime, in order to increase efficiency of a light signal of an illumination unit contained in the above-mentioned illumination system, a specific output angle, at which a luminous flux is maximally distributed, from among several output angles of the light signal generated from the light source should be used as a reference angle, such that the resultant light signal can be effectively applied to illumination lenses.
However, the above-mentioned illumination lenses have a rotational-symmetry structure and a fixed Etendue prescribed when the illumination device is designed, such that the light source is unable to use a desirable light signal in which a luminous flux is maximally distributed.
In order to employ the above-mentioned desirable light signal in which the luminous flux is maximally distributed, there are needed a plurality of illumination lenses, each of which has a large aperture, such that it is difficult to make a small-sized illumination device, resulting in deterioration of light efficiency.